1. Field of the Invention
The present invention relates to a display driving circuit and method, and, more particularly, to a display driving circuit and method capable of minimizing the residual image on a display panel as well as current consumption.
2. Description of the Related Art
Generally, liquid crystal display driving circuits and driving systems have used a technique of inserting black data into a liquid crystal display in order to remove a residual image on the liquid crystal display. The technique of inserting the black data and then driving valid data to remove the residual image on the liquid crystal display has a disadvantage in that current consumption greatly increases when the black data is inserted. In contrast, a technique of driving the valid data and then inserting the black data also has a disadvantage in that the electric current consumption greatly increases when the valid data is driven.
Here, the valid data means image data that is applied to a liquid crystal display panel to be actually realized, and the black data means data that is applied to remove a residual image effect occurring on the liquid crystal display panel.
FIG. 1 shows the voltage of the data applied to a continuous horizontal line in the technique of inserting black data and then driving valid data.
Referring to FIG. 1, when the i-th horizontal line ith of a liquid crystal display is activated, black data is inserted first, and then valid data is inserted. The next (i+1)-th horizontal line (i+1)th is activated in such a manner that black data is inserted and then valid data is driven. At this time, the polarities of the voltages applied to continuous horizontal lines are continuously changed. Although the valid data to be applied to the two subsequent horizontal lines have the same size, since the polarities of the voltages are reversed, the voltage corresponding to the i-th black data is depicted as it increases, and the voltage corresponding to the next (i+th) black data is depicted as it decreases.
In the case where the black data is inserted and then the valid data is driven so as to remove the residual image, current consumption increases through a quadrangular section indicated by a dotted-line when the black data is inserted. The insertion of the black data means that electric charges corresponding to the black data are charged into a corresponding pixel. Thus, while the electric charges are charged into the pixel (as indicated by the quadrilateral dotted-line), the electric current increases.
FIG. 2 shows the voltage of the data applied to a continuous horizontal line in the technique of driving valid data and then inserting black data.
Referring to FIG. 2, in order to remove the residual image, if the valid data is driven to than insert the black data, a current consumption rise section indicated by a quadrilateral dotted-line occurs when the valid data is driven.
FIG. 3 shows a technique of inserting black data using internal output buffers of a liquid crystal display driving circuit.
Referring to FIG. 3, the liquid crystal display driving circuit 300 includes multiple output buffers 301 to 304 installed thereinside, and multiple data selection switches SW1 to SWN connected to input stages of the respective output buffers 301 to 304, wherein the output buffers output signals output#1 to output#N to drive corresponding pixels (not shown), and each data selection switch switches one of valid data and black data.
FIG. 4 shows a technique of inserting black data using external output buffers of a liquid crystal display driving circuit.
Referring to FIG. 4, the liquid crystal display driving circuit 400 includes multiple output buffers 401 to 404 installed thereoutside and outputting signals output#1 to output#N to drive corresponding pixels (not shown), and multiple valid data selection switches SW11 to SW1N, input terminals of which are connected to output stages of the respective output buffers 401 to 404. Here, the output buffers. The other output terminals of the respective valid data selection switches SW11 to SW1N are connected to output terminals of respective black data selection switches SW21 to SW2N, through the other input terminals of which black data is supplied. Although not shown in FIG. 4, the black data may be replaced by direct current (DC) supply voltage.
Referring to FIGS. 1 through 4, it can be seen that, if the black data is inserted to then drive the valid data, the current consumption considerably increases when the black data is driven, and that, if the valid data is driven to then insert the black data, the current consumption also considerably increased when the valid data is driven.
In the case of semiconductor chips, high consumption power results in increasing temperature of the chip, which not only increases electric current consumption but also reduces a lifespan of the chip.